Hi all. I need some help on some problems I've been having. I have been printing shirts for a few months now with great success. I recently got some blue emulsion to replace my green speedball stuff and it has been working wonderfully. But up until last week I cant wash out any screens. I have been doing everything the same as always but now my screens won't wash out and I am thinking the emulsion went bad. I expose the screen using the same methods and techniques I have always used but now the screen won't wash out. I see the image burned into the screen but it doesn't "melt" away with ease like it used to. Now I have to spray really hard to get it to wash out. A pinhole sized hole appears and the emulsion comes off in chunks instead of melts. And by the time I get it to wash out, its so soggy it's unusable. Does anyone know how that could happen?
What kind of emulsion are you using. If you are having trouble washing out . . . then most likely you have overburned. I used a QX1 when I first started and it burned at 12 minutes. Then I switched to a different emulsion now it burns in 2.5 minutes. You just have to test a different times to see which burns the best. Best thing to do is created a step test in your program.
Do a search for step tests or step wedge test and you could get some helpful hints. I will save you money in the long run since emulsion can get pricey.
It's Murakami Photocure Blue, I've done a lot of exposures using this stuff and had it locked down. It took three minutes and gave me very consistent results. So yeah, been doing the same thing and all of a sudden it won't wash out. I even tried two minutes and then four minutes but acts the same way.
I think your screens are being "pre-exposed". Sometimes we'll have a screen that has managed to slip through the cracks so to speak and not get used for months and the constant running in and out of the dark room will cause this screen to be exposed to too much UV light prior to exposure. When this happens to us it is the exact symptoms that you described.
And, as others have already said, your burn time could be too long as well, but seeing that you have had success with that emulsion at that exposure time it sounds like something else. Let us know how this concludes.
Yeah that sounds possible. The last few times I was careful to block any light but again, I am just doing this out of my house and would be able to be exposed to a little bit of light.
One more question, After you've exposed the screen, do you have to take it directly to the wash out sink? I mean, I take it right to the sink to wash it out, is that ok? Or should i let it cool off because it's hot from being under the exposure light.
The emulsion is not old at all, its probably a month old. But I dont have a dark room, so when I apply the emulsion, its in my garage which is dark, but not darkroom dark. Maybe after so many trips, being exposed to that little amount of light each time, it got pre-exposed?
I would not put the emulsion at the top of the suspect list. This is a Pure Photopolymer emulsion that has a long shelf life and it seems you've handled it carefully. Did you by any chance replace the light bulb in your exposure fixture?
I don't understand how some have heat build up when exposing a screen, suggesting the need to use a fan. During exposure my screens may get warm but nowhere near hot.
Is the art any different? It could be a bad film. The film needs to be very opaque. A slight difference in the opacity can cause many problems in the screen room. Just a thought.
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Mike
If you dig ditches be the best ditch digger you can be.
If you see the image but it doesn't wash out, my first thought is overexposure. What is your light source? Have you tried reducing the exposure time, maybe by 1 minute to see what the results are?
My exposure time is three minutes. That time has been working well for me ever since I got the blue emulsion. I could go ahead and try one minute just to make sure I am covering all the bases.
Ahhh, sorry about that. I misunderstood what you typed. If it was working before and now it's not, then yes, I'd imagine the emulsion went bad, or is going bad. If you back your time off a little, you might be able to use it for a little longer.
I don't think the emulsion is bad. The shelf life for a coated screen is anywhere from 6 months or longer and it's 1-3 years for emulsion in the bucket. I bet if you coat some new screens and make absolutely sure no light hits them before exposure, your problem will go away. Your using a pure photopolymer so it doesn't take much light at all to ruin the screen. If you have a small crack in a doorway or ceiling tile or wherever, it will expose your screen.
Need help troubleshooting what went wrong! 
